1. Field of the Invention
The present invention relates to a position determination. More specifically, the present invention provides a position estimation system and method by a wireless communication network.
2. State of Technology
The maturing of integrated circuitry, micro-electromechanical systems (MEMS) and communication theory has precipitated the emergence of wireless networks and has led to the economic and computational feasibility of networks having a large number of self-sufficient and/or reliant nodes. Each node can be designed to, for example, sense elements of its environment, perform simple computations, and/or communicate with peer groups or directly to an external interrogator. In wireless network applications such as environmental monitoring of ground water or airborne chemicals, firefighters in buildings, or soldiers in caves, it is desirable to know the location of such network nodes independent of, for example, a Global Positioning System (GPS).
Background information on an existing technology that computes estimates of unknown locations of, for example, a radio terminal or a radio tag emitting a signal can be found in, U.S. Patent No. 2003/0174086 A1, titled “Determining a Time of Arrival of a Sent Signal,” issued Sep. 18, 2003 to Hirt, including the following: “The present invention provides a solution for determining a time of arrival tn, abbreviated to TOA, and if desirable, the absolute TOA, of one or a plurality of signals emitted by one or a plurality of transmitters, e.g. terminals or radio tags, and receivable at different location of known spatial coordinates. In particular, the solution is based on measuring and comparing the total signal transfer time (TSTT) of signals, in such a way that explicit knowledge of absolute time or absolute time synchronization between components located at different spatial positions is not required.”
Background information on a system and method that utilizes peer-to-peer proximity measurements together with a known geographical position can be found in, U.S. Pat. No. 6,473,038 B2, titled, “Method and Apparatus for Location Estimation,” issued Oct. 28, 2002 to Patwari et al., including the following: “a system and method operate to provide location estimates for mobile devices. The system does not require a great deal of installed infrastructure. Moreover in the case of urban canyons and inside buildings where there are numerous obstructions to the propagation of signals (e.g., GPS signals), the system is able to function to provide location information for devices that might otherwise be out of range.”
Background information on a system that utilizes Ultra Wideband (UWB) or short pulses to estimate the position of a receiver by measuring the one-way flight time of a pulse sent from multiple independent transmitters can be found in, U.S. Pat. No. 6,054,950, titled, “Ultra Wideband Precision Geolocation System,” issued Apr. 25, 2000 to Fontana, including the following, “The system includes a set of N (where N>2) untethered UWB transceivers located at fixed positions, an untethered UWB receiver at the target, and a processor at the target for resolving time-of-flight measurement ambiguities of received pulses to determine precise geolocation by solving a set of equations according to time-of-flight measurements and surveyed positions of N−1 transceivers.”
Background information on a system that utilizes transmitted and received pulse trains to measure distances between radio devices can be found in, U.S. Pat. No. 6,674,396 B2, titled, “System and Method For Distance Measurements by Inphase and Quadrature Signals in A Radio System,” issued Jan. 6, 2004 to Richards et al., including the following, “the key to measuring a distance according to the present invention is to precisely measure the time it takes for a single bit to travel from a first radio transceiver to a second radio transceiver. Since in reality it is difficult to transmit and receive a single bit, the distance is measured by determining the time it takes a pulse train to travel from a first radio transceiver to a second transceiver and then from the second radio transceiver back to the first radio transceiver. Stated in other terms, the distance is measured by determining the travel time for a complete exchange of data between the first and second radio transceivers.”
Background information on a system that utilizes beacons to determine a location of mobile units can be found in, U.S. Patent No. 2003/0028323, titled, “Material Handling Systems with High Frequency Radio Location Devices,” issued Feb. 6, 2003 to Zeitler et al., including the following, “A material handling system uses high-frequency location devices for determining the location of mobile units, such as AGV's, overhead mono-rails, conveyor components, or individual articles being transported by such devices . . . The location devices work in cooperation with a number of stationary location devices, such as beacons, that are positioned within the environment at known locations, such as in or adjacent the ceiling of the workplace environment.”
Accordingly, the present invention provides a wireless localization solution by a method and system that includes statistical processing of time of flight information to estimate a position of a receiving device.